Field of the Invention
The present specification discloses a method of transmitting network assistance information for removing interference, and a serving cell base station.
Related Art
A 3rd generation partnership project (3GPP) long term evolution (LTE) that improves a universal mobile telecommunications system (UMTS) has been introduced to a 3GPP release 8. The 3GPP LTE uses an orthogonal frequency division multiple access (OFDMA) in a downlink and a single carrier-frequency division multiple access (SC-FDMA) in an uplink. The OFDM needs to know in order to understand the OFDMA. The OFDM may be used since an inter-symbol interference effect can be reduced due to low complexity. The OFDM converts data to be input in serial into N parallel data and transmits it by carrying N orthogonal sub-carriers. The sub-carriers maintains orthogonally in a frequency dimension. Meanwhile, the OFDMA means a multiple access method to realize multiple accesses by providing a part of the available sub-carrier to each user independently, in a system using the OFDM in a modulation scheme.
Meanwhile, in general, information, e.g., data, is easily distorted and changed when transmitted through a wireless channel. Therefore, a reference signal (RS) is required to demodulate such information in an error-free manner. The RS may be divided into a common RS (CRS) and a user equipment (UE)-specific RS according to whether it is used in common. In addition, according to a usage, the RS may be divided into a demodulation RS (DM-RS) and a channel state indicator RS (CSI-RS).
The CSI-RS is transmitted by a base station (BS) to a UE. On the basis of the CSI-RS, the UE feeds back information indicating a channel state such as CQI/PMI/RI to the BS.
However, a CSI-RS from a neighbor cell may act as interference to the UE according to a situation.
In particular, recently, there is an ongoing discussion on a heterogeneous network in which a macro cell and a small cell co-exist, and due to such a small cell, interference may be more and more increased. Therefore, an interference cancellation capability is desperately required.